Carbon dioxide in coal

White C. Sequestration of carbon dioxide in coal with enhanced coalbedmethan re-covery-a review. 2005 Energy Fuels 19(3) 659-724. 

Chlorine is the as-determined chlorine (ASTM D-2361 ASTM D-4208), Sp is the as-determined pyrite sulfur (ASTM D-2492), S03ash is the as-determined sulfate (sulfur trioxide, S03) in ash (ASTM D-1757), and C02 is the as-determined carbon dioxide in coal (ASTM D-1756). All other terms are as given in the earlier formulas, and all values are expressed as percentages. 

One particular test method (ASTM D-1756) covers the determination of carbon dioxide in coal in any form, such as mineral carbonate, from which carbon dioxide is released by action of mineral acids (e.g., hydrochloric acid). The method can be applied to high- and low-carbonate coals. The determination of carbon dioxide is made by decomposing with acid a weighed quantity of the sample in a closed system and absorbing the carbon dioxide in an absorbent (e.g., such as sodium... 

Three methods for determining mineral carbon dioxide in coal were investigated using bituminous coal. The titrimetric method is claimed to be superior to either of the then-used British standard gravimetric or manometric methods (BS 1016). The procedure involves the decomposition of carbonate minerals with hydrochloric acid and absorption of the evolved carbon dioxide in a mixture of benzylamine, ethanol, and dioxan. This mixture forms a stable salt of benzylcar-bamic acid, which is then titrated with sodium methoxide. The method was said to be suitable for all concentrations of carbon dioxide. It is especially accurate for low concentrations, and it is much more rapid than other methods tested. 

Figure 3.8 Schematic of storage of carbon dioxide in coal seams/ (Courtesy of the International Energy Agency).

Recently, significance of coal petrology has been demonstrated in CBM exploration and in potential sequestration of carbon dioxide in coal seams. Techniques developed in the study of coal are also used in the investigation of organic-rich rocks to evaluate source rocks in petroleum and natural gas exploration. 

In combination, carbon is found as carbon dioxide in the atmosphere of the earth and dissolved in all natural waters. It is a component of great rock masses in the form of carbonates of calcium (limestone), magnesium, and iron. Coal, petroleum, and natural gas are chiefly hydrocarbons. 

In 1990, a test using scrap tires (2x2 in. I DE) to generate steam for electricity was conducted at the Elexsys plant. The I DE replaced 20% of the plant s coal. Results showed that IDE is an environmentally sound fuel. Particulate emissions were reduced by the lower ash content of IDE, volatile organic compounds (VOC) were reduced because of more efficient burning of I DE compared to coal, and carbon dioxide emissions were reduced because I DE contains half the fixed carbon found in coal. Nitrogen oxide, chlorine emissions, and metals were also reduced, and ferrous metals and dioxins were nondetectable (7). 

The radiation from a flame is due to radiation from burning soot particles of microscopic andsubmicroscopic dimensions, from suspended larger particles of coal, coke, or ash, and from the water vapor and carbon dioxide in the hot gaseous combustion products. The contribution of radiation emitted by the combustion process itself, so-called chemiluminescence, is relatively neghgible. Common to these problems is the effect of the shape of the emitting volume on the radiative fliix this is considered first. 

The most likely substitute for coal is natural gas, which, as noted earlier, releases about 55 percent of the amount of carbon dioxide that coal, on the average, does. In addition, it produces far fewer other pollutants, such as sulfates and polycyclic hydrocarbons, than coal and oil yield on combustion. 

The process will adversely affect air quality by releasing nitrogen oxides, sulfur oxides, carbon monoxides and other particulates into the atmosphere. Better control of the conversion conditions and better control of emissions can make the process cleaner, yet technology cannot do anything to curb carbon emissions. Since much of the carbon in coal is converted to carbon dioxide in the synthesis process, and is not part of the synthetic fuel itself, the amount of carbon dioxide that will be released to the environment during combustion is 50 to 100 percent more than coal, and around three times more than natural gas. 

Damle, A.S., Separation of Hydrogen and Carbon Dioxide in Advanced Fossil Energy Conversion Processes using a Membrane Reactor, 2002 Pittsburgh Coal Conference, Pittsburgh, PA, September 2002. 

When the earth was formed about 4.5 billion years ago, 95% of the atmosphere consisted of carbon dioxide. The emergence of plant life changed the atmosphere since plants, through the process of photosynthesis, absorb carbon dioxide. Carbon from the atmosphere was absorbed into the vegetation and when the vegetable matter died, it decomposed, and formed coal and oil. This dropped the carbon dioxide in the atmosphere to less than 1%. 

Other early workers in this field include Briggs and Sinha 61), who measured the effect of carbon dioxide on coal and McBain et al. 6 ), who adsorbed water, heptane, and benzene on sugar charcoal. 

The oil, coal, and natural gas we burn for energy are made up mostly of carbon. Our dependence on these fuels has, in recent years, caused economic problems, but even more importantly, it has contributed to the worldwide problem of global warming. Most scientists now believe that the burning of carbon-based fuels has increased the concentration of carbon dioxide in the atmosphere, and that this, in turn, has resulted in rising... 

About 1865, E. Kopp, and P. W. Hofmann tried to revive the oxysulphide theory, but J. Pelouze refuted their arguments and after a long study of the reactions, J. Kolb confirmed A. Scheurer-Kestner s work, but concluded that in the main reaction the calcium carbonate loses its carbon dioxide by the action of the carbon dioxide in the fire gases. A. Scheurer-Kestner then showed that in this last conclusion J. Kolb is in error, because black ash can be made in crucibles without any assistance from the fire gases that the decomposition of the calcium carbonate, even in the presence of coal, requires a higher temp, than the reduction of the sodium sulphide and that black asb is obtained by directly heating sodium sulphide with calcium carbonate. 

An important variant of the Fluid Bed system is under development. This variant eliminates use of air or oxygen in the actual gasifier. Steam and coal are the reactants. Since we know from Table 3 that the reaction of steam with coal is endothermic, a heat source must be provided. Hot solids in the form of char are heated in a combustor and are transferred to the gasification reactor as one these processes. In another, hot alkaline oxides react with the carbon dioxide in the gas to form carbonates. The exothermic reaction of carbonate formation supplies the heat requirements of the steam-carbon reaction. Both of these processes depend on a reactive coal or char to implement the steam-carbon reaction. 

The actual proportion of carbon dioxide in the air varies very considerably according to circumstances. Whalley reported that in a Scottish mine the carbon dioxide in the air near the coal face reached T21 per cent., whilst on the pavement it was no less than 4-56 per cent. Levy,1 in discussing the abnormal air of New Granada, points out that owing to forest fires the percentage of carbon dioxide in the air would often rise to 0-49 per cent. These cases, however, are abnormal. 

---